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I had a .net 1.1 app fail after installing .net 4.0, and I don't know if 4.0 is the cause. At the very end of 1.1's machine.config, the app was reporting an error unrecognized system.data section. (I ran it in vs2008 debugger to find this.) I commented out the section, it was empty anyway, and the app started to run again. The app has been running correctly for years, on xp, vista and win7-64.

This is the section in machine.config causing the problem:

<system.data>
  <DbProviderFactories></DbProviderFactories>
</system.data>
P a u l
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  • Are you asking if the mere installation of .NET 4 will update all existing .config files? Did you do anything to cause the .config file to be updated? I'm not sure what you're asking. – David Hoerster Feb 22 '11 at 18:59
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    Can you paste the code that's causing the issue? – AndrewC Feb 22 '11 at 18:59

3 Answers3

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Installing any version of .NET other than 1.1 can certainly break .NET 1.1 applications. This is because Microsoft fixed several bugs in .NET 1.1 in a breaking manner. I believe that installing .NET 4.0 will also install one or more of those service packs for .NET 1.1, so you could see one of the breaks.

John Saunders
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Just in case things may be GAC related, see:

.NET 4.0 has a new GAC, why?

Also, is it possible that the unrecognized system.data section in the machine.config was placed there manually? And didn't make trouble until the CLR 4.0 was installed?

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rskar
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  • And watch out once you start using Visual Studio 2010 or newer. Unless you use the .NET 4.0 version of `gacutil` to manage your GAC'ed DLLs, you're likely to encounter warning MSB3258: "The primary reference has an indirect dependency which has a higher version "4.0.0.0" than the version "..." in the current target framework.", which can be REALLY hard to figure out. Trust me :-) – Ross Patterson Sep 20 '12 at 16:41
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Microsoft has stated that all versions of .Net can be installed in parallel without interfering with each other (at least thats what they said at MSDN Live). Each version is installed in a separate directory.

If you are talking about ASP.Net then you must consider what version your application is configured for in IIS.

Tedd Hansen
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